In order to preserve the inheritance chain, the Super Type (property sling:resourceSuperType) of the overlay components are set to the same value as the Super Type of the components being overlaid, in this case

social/commons/components/comments

social/commons/components/comments/comment

The overlay's own Type (property sling:resourceType) must be a relative self-reference so that any content not found in /apps is then looked for in /libs.

select node /apps/social/commons/components/hbs/comments

in the entry area at the bottom of the Properties tab, type the following values for a new property: